The European Data
Format
(EDF)
is a simple and
flexible format for
exchange
and storage of multichannel biological and physical signals. It
was developed
by a few European 'medical' engineers who first met at
the 1987 international Sleep Congress in Copenhagen. The EDF logo is
derived
from the
congress logo which was the green pea
from the fairy tale "The princess and the pea" by the Danish
writer Hans Christian Andersen. With the support of
the late professor Annelise
Rosenfalck from Aalborg university, the engineers initiated the project "Methodology for the Analysis of the Sleep-Wakefulness Continuum" (1989-1992) that was funded by the European Community through its "Comité d'Action Concertée" (COMAC committee) on Biomedical Engineering. They
wanted to apply their sleep analysis algorithms to each others data and
compare the analysis results. So, on a morning in Leiden in March 1990,
they agreed upon a very simple file format to exchange their sleep recordings. This format
became known as the European Data Format. In August 1990, all
participating labs had contributed an EDF sleep recording to the
project.
EDF was
published in
1992 in Electroencephalography
and Clinical Neurophysiology 82, pages
391-393. Since then, EDF became the de-facto standard for EEG and PSG
recordings
in commercial
equipment and multicenter research projects.

An extension of EDF, named EDF+, was developed in 2002 and is largely compatible
to
EDF: all
existing EDF viewers also show EDF+ signals. But EDF+ files can also
contain interrupted recordings, annotations, stimuli and events.
Therefore, EDF+ can store any medical recording such
as EMG, Evoked potentials, ECG, as
well as automatic and manual analysis results such as deltaplots, QRS
parameters and sleep stages.The specs are stricter
than EDF which enables automatic
localization and calibration
of electrodes. And EDF+ fixed a few omissions in EDF such as the Y2K problem,
little-endian integers, and comma vs dot.

EDF+ was published in2003 in Clinical
Neurophysiology 114, pages 1755-1761. Since then, hundreds of EDF+
files and several EDF+ viewers became available on the internet. Applications are mainly in Clinical Neurophysiology, Sleep,
and Cardiology. Formal standards from
other specialisms
can also be integrated into EDF+.
Most EDF applications have migrated to EDF+.
EDF and EDF+ are freely available without charge. The full
specifications are in the above-mentioned publications as well as on
this EDF website. The site also supports users and developers by
offering free downloads of files and software, a list of EDF(+)
compatible companies and further contact possibilities such as Yahoo's
EDF group.

EDF(+) recordings and software are most welcome, as are companies and
developers that support EDF(+).